This invention relates to irrigation drip or trickle tubing. In recent years, irrigation drip tubing has become popular to increase agricultural yields. Accurate watering of the root areas of plants causes an improved growth rate and the lack of watering between plants reduces weeds. Concentrated irrigation also gives maximum utilization of available water, and the tubing itself can be used to meter liquid fertilizers, pesticides and soil conditioners.
The basic concept of irrigation tubing is sound but the design of the tubing should meet certain practical criteria. Because plants may be spaced unevenly, it is often highly desirable to have a variable means for determining the location of the outlet apertures and the flow therethrough. That is, the outlets of the irrigation tubing should be available on a basis of need rather than on any predetermined manufactured spacing. Maturing young orchards are a specific example of a crop that may require additional outlets in irrigation tubing over a period of time.
It is also highly desirable to provide a pressure reduction means within the tubing in order to permit the water to drip out at a predetermined rate regardless of the outlet aperture size. Insects have been known to enlarge outlet apertures in irrigation tubing by chewing the edges thereof. Alternately, impurities in the water may also reduce the outlet sizes. If the drip rate is dependent on outlet size, undesirably high flow rates result. Drip irrigation tubing should also be economical to manufacture, soundly designed and easy to put into operation. For example, large appendages extending from the tubing should be avoided as should any design requiring hand assembly.
Previous irrigation tubing has attempted to satisfy the requirements involved but have been deficient in some respect. For example, some outlet openings on prior art tubing are placed in a tubular member at the time the tubing is put into operation in the field. This field operation is time consuming and carelessness could cause water to enter the field at a higher or lower rate than desired and in the wrong location. The size of the outlet opening is not adequately uncontrollable and the resulting flow rates may differ considerably.
In systems where the irrigation drip holes in the outer tubular member are made at the time of manufacture, irrigation occurs uniformly along the entire length of the tubing. Thus, where plants are not evenly distributed, water is used unnecessarily. Many irrigation systems also use the size of the outlet aperture to control flow rate and encounter the above-noted insect problem.
This invention has the advantage of variable flow rates at a given location. The use of a plurality of removable bosses over outlet apertures allows irrigation only where desired and at different rates. The design and size of the tortuous path of this invention and not the sizes of the inlet or outlet aperture are used to govern the flow rate. Insect damage to or accidental enlargement of the outlet apertures does not vary the flow. A particular feature of this invention is the use of closely spaced paired outlet apertures fed by separate oppositely directed passageways. The outlet flow rate may thus be adjusted by a factor of two and, alternately, one aperture may be reserved in case the other one clogs. A separate inlet aperture is used to feed each passageway and thus isolates any obstruction. This tubing is also economical to manufacture and put into operation. No special hand fitting is required.